The postdoctoral research training program in Endocrinology and Diabetes at the Massachusetts General Hospital is intended to provide intensive research experience in basic or clinical investigation, complemented by didactic research training in basic sciences pertinent to endocrinology and diabetes. The trainees are primarily M.D.'s and M.D./Ph.D.'s who desire a career in investigative endocrinology and academic medicine, as well as Ph.D.'s who want further research training. The trainees are selected from a large applicant pool on the basis of prior academic and/or research achievement, and evidence of strong commitment to a career in biomedical investigation. The Program director (J. Avruch) is a senior academician/endocrine investigator who governs in conjunction with a committee of experienced endocrine scientists (Habener, Kronenberg, Crowley, Neer, Freeman and Klibanski). The training faculty consists of 46 active, well-funded scientists, whose interests range broadly across the subdisciplines of endocrinology, and from clinical investigation to the regulation of gene expression, protein structural analysis, transmembrane signaling mechanisms, etc. The trainees are supervised closely by a primary faculty mentor, and interact extensively with junior faculty, who often serve as secondary mentors. A carefully evolved and extensive program of didactic sessions complements the research activity. The training period is 2-3 years but may include several years additional experience at junior faculty status, so as to permit consolidation of skills and maximal competitiveness for independent support. The productivity of past trainees during training has been very high overall, as judged by the number and quality of trainee publications. Among the program graduates since 1990 supported by this grant, the majority remain in academia and a substantial number are in the biotechnology/pharmaceutical industry. Among those in academia, about one quarter have achieved independent support equivalent to an RO-1 and nearly one third have achieved transitional independent support, a usual precursor to RO-1 support. The facilities at the MGH are extensive, including an active GCRC, an Institutional Clinical Research Support Program, access to a very large base of endocrine/diabetes patients, and over 40,000 square feet of fully equipped modern laboratory dedicated to our training faculty. The institutional training grant represents the central stabilizing financial element in this program, and is especially critical in enabling M.D. trainees to achieve careers in biomedical investigation.